Such ion implantation technique may be used for production of all types of semiconductor devices, such as for example different types of diodes, transistors and thyristors, and it is an attractive technique in device fabrication as it allows room temperature control of both impurity level and distribution. This technique is well developed for Si-devices, but the method successfully used for ion implantation for such devices may not be utilized for SiC-devices, which are particularly used in applications in which it is possible to benefit from the superior properties of SiC in comparison with primarily Si, namely the capability of SiC to function well under extreme conditions. SiC has a high thermal stability due to a large bandgap energy, so that devices fabricated from the material are able to operate at high temperatures, namely up to 1000 K. Furthermore, it has a high thermal conductivity, so that SiC devices may be arranged at a high density. SiC also has a more than five times higher breakdown field than Si, so that it is well suited as a material in high power devices operating under conditions where high voltages may occur in the blocking state of a device.
Accordingly, it is highly desired to find means to control this technique of device fabrication also for SiC, so that doped high quality regions with a low defect density may be created in SiC by ion implantation.
U.S. Pat. No. 3,629,011 describes a method according to the introduction, in which ions are implanted in SiC at room temperature, and the implanted near surface layer is then annealed at a temperature between 1200 and 1600.degree. C. for electrically activating the impurity atoms implanted. It has turned out that the crystaline quality of the near surface layer thus created is not as high as desired and achievable by using the ion implantation technique for fabricating devices of Si.
It has also been discussed to carry out the ion implantation at such a dose that an amorphous near surface layer is formed and then anneals this layer, which has been successful in the technique of device fabrication in Si, since the amorphous layer will, during the annealing, be subjected to a "solid phase-epitaxy" or an epitaxial regrowth of the layer resulting in a high quality recrystallized layer, but it has turned out that this technique would be useless for SiC, since the annealing of this amorphous layer will result in polycrystalline forms of silicon carbide or defective single crystals of silicon carbide.